/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.tencent.angel.ipc;

import com.google.protobuf.RpcCallback;
import com.google.protobuf.RpcController;
import com.tencent.angel.utils.StringUtils;
import java.io.IOException;

/**
 * Used for server-side protobuf RPC service invocations. This handler allows invocation exceptions
 * to easily be passed through to the RPC server from coprocessor
 * {@link com.google.protobuf.Service} implementations.
 *
 * <p>
 * When implementing {@link com.google.protobuf.Service} defined methods, coprocessor endpoints can
 * use the following pattern to pass exceptions back to the RPC client: <code>
 * public void myMethod(RpcController controller, MyRequest request, RpcCallback<MyResponse> done) {
 * MyResponse response = null;
 * try {
 * // do processing
 * response = MyResponse.getDefaultInstance();  // or use a new builder to populate the response
 * } catch (IOException ioe) {
 * // pass exception back up
 * ResponseConverter.setControllerException(controller, ioe);
 * }
 * done.run(response);
 * }
 * </code>
 * </p>
 */
// TODO: 17/6/30 by zmyer
public class ServerRpcController implements RpcController {
    /**
     * The exception thrown within {@link com.google.protobuf.Service#callMethod(com.google.protobuf.Descriptors.MethodDescriptor,
     * com.google.protobuf.RpcController, com.google.protobuf.Message,
     * com.google.protobuf.RpcCallback)} , if any.
     */
    // It would be good widen this to just Throwable, but IOException is what we
    // allow now
    private IOException serviceException;
    private String errorMessage;

    @Override
    public void reset() {
        serviceException = null;
        errorMessage = null;
    }

    @Override
    public boolean failed() {
        return (failedOnException() || errorMessage != null);
    }

    @Override
    public String errorText() {
        return errorMessage;
    }

    @Override
    public void startCancel() {
        // not implemented
    }

    @Override
    public void setFailed(String message) {
        errorMessage = message;
    }

    @Override
    public boolean isCanceled() {
        return false;
    }

    @Override
    public void notifyOnCancel(RpcCallback<Object> objectRpcCallback) {
        // not implemented
    }

    /**
     * Sets an exception to be communicated back to the {@link com.google.protobuf.Service} client.
     *
     * @param ioe the exception encountered during execution of the service method
     */
    public void setFailedOn(IOException ioe) {
        serviceException = ioe;
        setFailed(StringUtils.stringifyException(ioe));
    }

    /**
     * Returns any exception thrown during service method invocation, or {@code null} if no
     * exception was thrown. This can be used by clients to receive exceptions generated by RPC
     * calls, even when {@link com.google.protobuf.RpcCallback}s are used and no {@link
     * com.google.protobuf.ServiceException} is declared.
     */
    public IOException getFailedOn() {
        return serviceException;
    }

    /**
     * Returns whether or not a server exception was generated in the prior RPC invocation.
     */
    private boolean failedOnException() {
        return serviceException != null;
    }
}
